1. Field
Embodiments of the present invention pertain to the field of automate process control, and in particular, to metrology and control of epitaxially grown material layers in a light emitting diode (LED) film stack.
2. Description of Related Art
Group III-V materials are playing an ever increasing role in the semiconductor device and related, e.g. light-emitting diode (LED), industries. While devices such as LEDs employing multiple quantum well (MQW) structures epitaxially grown on a substrate are a promising technology, epitaxial growth of such structures is difficult because of the very thin material layers formed and the dependence of device properties (e.g., emission wavelength) on the material and physical characteristics of those layers.
The material and/or physical characteristics of an MQW structure are dependent on the growth environment within an epitaxy chamber. Post-manufacture metrology of an LED material stack provides a manufacturing control point which too far downstream to avoid significant yield loss in the event one of the epitaxial growth processes forming the LED stack deviating out of specification. In-situ metrology of an LED material stack however is prohibitive because of the epitaxy chamber and environment therein obscures observation of material properties.